Re: automatic undo management vs rollback segs (9i)

> Apparently 9i has some new version of rollback segments called undo> management.> Does anyone have any experience with this and is it worth using.

I use nothing but automated UNDO. I can't imagine going back to the old
rollback segments. Undo segments have worked great for me and it is a
relief that I don't have to worry about rollback segments any more. I
haven't experienced any problems from them either except for the
occasional ORA-1555 (snapshot too old) error when my UNDO_RETENTION was
not sufficiently high enough.

>I run> a small DB> < 3G total not tons of transactions or concurrnet users> If it is good does the tablespace reside on SYSTEM tablespace and can> you change that since Oracle has always advised against using SYSTEM> for anything other than Oracle Stuff.

You have to create a special tablespace called an UNDO tablespace. You
create it with the CREATE UNDO TABLESPACE command. Then you set your
UNDO_TS parameter to this tablespace name. You also set UNDO_MANAGEMENT
to AUTO and set your UNDO_RETENTION.

You cannot use the SYSTEM tablespace for automated undo.

I would highly recommend that you read the Oracle docs on the subject...

> If it not a great new tool do you use the same old methods to create> Rollback segments as before (8.1.5). ie

I don't use the old rollback segments any more.

> Use the system rollback for early instance and database creation> then> create an additional RBS on system and bring online> run catalog.sql and catproc.sql> create tablespaces including an RBS tablespace> create new RB segs and bring system rollback seg offline> shutdown and restart instance with new parameter file with> RB1,RB2....RBn uncommented which will bring them all online

When you create a database, the CREATE DATABASE command can also create
the UNDO tablespace at the same time. The syntax now allows for this.

> ? has that changed if you decide to use UNDO_MANAGEMENT = MANUAL

If you are using manual undo management, ie. the old rollback segments,
then nothing has changed.

HTH,
Brian

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